Artificial turf with textured yarn and production method

ABSTRACT

The method of manufacturing a textured artificial turf yarn includes providing a monofilament yarn, wherein the monofilament yarn includes a polymer blend of polymers; receiving differential scanning calorimetry, DSC, data of a sample of the polymer blend; determining one or more melting temperatures of the monofilament yarn using the DSC data; and texturing the monofilament yarn within a chosen temperature range using a texturing device to provide a textured artificial turf yarn, wherein the chosen temperature range is selected using the one or more melting temperatures.

FIELD OF THE INVENTION

This invention relates to artificial turf, and more particularly to anartificial turf with textured yarn and to a production method fortextured yarn.

BACKGROUND AND RELATED ART

Artificial turf or artificial grass is a material that is made up offibers used to replace natural grass. The structure of the artificialturf is designed such that the artificial turf has an appearance whichresembles natural grass. Typically artificial turf is used as a surfacefor sports such as soccer, American football, rugby, tennis, golf, andfor playing fields or exercise fields. Furthermore, artificial turf isfrequently used for landscaping applications.

Artificial turf may be manufactured using techniques for manufacturingcarpets. For example, artificial turf fibers which have the appearanceof grass blades may be tufted or attached to a backing. Artificial turfdoes not need to be irrigated or trimmed and has many other advantagesregarding maintenance effort and other aspects. Irrigation can bedifficult due to regional restrictions for water usage. In otherclimatic zones the re-growing of grass and re-formation of a closedgrass cover is slow compared to the damaging of the natural grasssurface by playing and/or exercising on the field. Artificial turf doesnot need sunlight and thus can be used in places where there is notenough sunlight to grow natural grass. To ensure that artificial turfreplicates the playing qualities of good quality natural grass,artificial turf needs to be made of materials that will not increase therisk of injury to players and that are of adequate durability. Manysports fields are subjected to high-intensity use relating toplayer-to-surface interactions and ball-to-surface interactions. Thesurface of the artificial turf fibers must be smooth enough to preventinjuries to the skin of the players when sliding on the surface, but atthe same time must be sufficiently embedded into the substructure toprevent the fibers from coming loose. Thus, the materials used forproducing artificial turf must have highly specific properties regardingsmoothness, brittleness, resistance to shear forces, etc.

SUMMARY

The following definitions are provided to determine how terms used inthis application, and in particular, how the claims, are to beconstrued. The organization of the definitions is for convenience onlyand is not intended to limit any of the definitions to any particularcategory.

A “polymer blend,” as understood herein, is a mixture of polymers, whichcan have different types (e.g., different types of polyethylene). Thepolymer blend can comprise various additives added to the polymermixture. The polymer blend can be at least a three-phase system. Athree-phase system as used herein encompasses a mixture that separatesout into at least three distinct phases. The polymer blend can comprisea first polymer, a second polymer, and a compatibilizer. These threeitems form the phases of the three-phase system. If there are additionalpolymers or compatibilizers added to the system then the three-phasesystem may be increased to a four, five, or more phase system. The firstpolymer and the second polymer are immiscible. The first polymer formspolymer beads surrounded by the compatibilizer within the secondpolymer.

The term “polymer blend,” as understood herein, encompasses the term“polymer mixture”. The term “blend,” as understood herein, encompassesboth a physical mixture of polymer particles on a macroscopic scale anda dispersion of polymers on a molecular scale.

The terms “polymer bead” and “beads” may refer to a localized region,such as a droplet, of a polymer that is immiscible in the secondpolymer. The polymer beads may in some instances be round or sphericalor oval-shaped, but they may also be irregularly shaped. In someinstances the polymer bead will typically have a size of approximately0.1 to 3 micrometers, preferably 1 to 2 micrometers in diameter. Inother examples, the polymer beads will be larger. They may, forinstance, have a diameter up top 50 micrometers.

A polymer blend may also be composed of compatible and misciblepolymeric components. Compatibility means, as understood herein, thatblending of, e.g., two distinct polymers, leads to an enhancement of atleast one desired property, when comparing the blend to one of the twoindividual blend components. Ideally, the performance of the blend liesin between the range, which is flanked by the two blend components, infact, in strong relationship to the concentration ratio. However,compatibility is only given in some exceptional cases, mostly related tocompletely amorphous polymers. In nearly all other polymer mixtures, anenhancement of properties fails and the resulting blend stays far behindthe property profile of the involved blend components. Polymermiscibility, as used here, is meant in a thermodynamic sense and can becompared to solubility. Completely miscible polymers form a single phasecontinuity upon mixing, i.e., one component is fully dispersed in theother component. This is in most cases true for amorphous polymers, butit is a rare case for semi-crystalline polymers. Complete miscibilitywould also require co-crystallization of the crystalline phase. Thisexplicitly would affect the melting behavior of polymeric blends.

The term “polymorphism” or “polymorphic modification,” as used herein,refers to the fact that solid matter is able to exist in different formsof crystal structures. This may include not only differentcrystallographic unit cells but different crystal imperfections as well.

The “melting temperature” is, as understood here, a characteristictemperature of a polymer blend, at which at least a portion of acrystalline fraction of one of the polymers of the polymer blend melts.In the case when a crystalline fraction of the polymer of the polymerblend has polymorphism, then the polymorphic modification of the polymerhaving polymorphism has a respective melting temperature at which atleast a portion of the polymer has polymorphism. Melting at the meltingtemperature is a process wherein the thermal energy in a crystallinefraction of a polymer is sufficient to overcome the intermolecularforces of attraction in the crystalline lattice so that the latticebreaks down and at least a portion of the crystalline fraction becomes aliquid, i.e., it melts. Further in the text, the term “meltingtemperature” of a polymer refers to a melting process of its crystallinefraction without explicit reference to the latter. This formulation isin conformity with the general practice, because purely crystallinepolymers are very rarely used and are quite difficult to produce.

The “sigmoid (sigmoidal) function” is, as understood here, a limitedfunction having non-positive or non-negative derivative and acharacteristic S-shaped curve. The sigmoid function can be, forinstance, the logistic function expressed by the following formula:S(x)=1/(1+exp(−x)).

Utilization of textured (curled) yarns in artificial turf carpets mayprovide for the above-mentioned required properties of the artificialturf carpets. Textured yarns are different from flat monofilament yarnsin that they are irregularly crimped. The textured yarns exhibit azig-zag shape having at least one of the characteristic features such askinks, jogs, bends, crinkles, buckling, and curls. These features makethe textured yarns more voluminous and soft when manufactured intoartificial turf, compared to flat monofilament fibers. The textured yarnmay also be advantageous over flat yarn concerning the capability ofholding infill material in its place, i.e. reducing the splash of infillmaterial when, e.g. a ball hits the ground.

The invention provides for an artificial turf carpet, a method ofmanufacturing the artificial turf carpet, a textured (curled) artificialturf yarn, and a method of manufacturing the textured (curled)artificial turf yarn as formulated in the independent claims.Embodiments are given in the dependent claims.

In one aspect the invention provides for a method of manufacturing atextured artificial turf yarn using a texturing device and a controlleroperable to hold an actual temperature of a texturing process in thetexturing device at a desired temperature, wherein the method comprises:providing a monofilament yarn, wherein the monofilament yarn comprises apolymer blend of polymers; receiving differential scanning calorimetry(DSC) data of a sample of the polymer blend; determining one or moremelting temperatures of the monofilament yarn using the DSC data;determining a desired temperature of the texturing process using the oneor more melting temperatures; and texturing the monofilament yarn usingthe texturing device to provide the textured artificial turf yarn,wherein the controller is programmed to hold the actual temperature atthe determined desired temperature. The monofilament yarn may have, forinstance, a width of 1-1.1 mm and a thickness of 0.09-0.11 mm. Themonofilament yarn weight may typically reach 50-3000 dtex. The DSC datacan be measured by using a DSC system.

Utilization of the DSC data may be advantageous, because it may providefor a melting temperature of the polymer (or its particular polymorphicmodification) in the polymer blend. As discussed further in greaterdetail, the texturing (curling) of the monofilament yarn may beperformed within the temperature range, in which at least a portion of acrystalline fraction (or of a polymorphic modification) of at least oneof the polymers of the polymer blend remains in a solid state. Thus theknowledge of the melting temperatures determined using DSC data mayprovide for the temperature range that may be optimal for the texturing(curling) process.

In another embodiment, the desired temperature of the texturing processis determined such that a portion of a crystalline fraction of thepolymer blend is in a solid state in a process of the texturing(curling) of the monofilament yarn and another portion of thecrystalline fraction of the polymer blend is in a molten state in theprocess of the texturing (curling) of the monofilament yarn.

This embodiment may be advantageous because it may provide for anoptimal process temperature, wherein at least a portion of each of thepolymers (or their polymorphic modifications) of the polymer blend is ina molten state. The portion of the crystalline fraction that is moltencan be more than 10% (preferably 25%) by weight of the entirecrystalline fraction. The portion of the crystalline fraction thatremains solid can be more than 10% (preferably 25%) by weight of theentire crystalline fraction.

In another embodiment, the desired temperature of the texturing processis determined such that a crystalline fraction of one of the polymers iscompletely or almost completely in a solid state in a process of thetexturing of the monofilament yarn and a crystalline fraction of anotherone of the polymers is completely or almost completely in a molten statein the process of the texturing of the monofilament yarn.

This embodiment may be advantageous because it may provide for a morerobust process temperature, wherein at least one crystalline fraction ofthe respective polymer remains completely or almost completely in asolid state during the texturing (curling) process. Selecting thetexturing process temperature as specified in this embodiment providesfor an improved stability and repeatability of the texturing process,because in the texturing process the crystalline fraction of one of thepolymers is completely in a solid state and the crystalline fraction ofthe other one of the polymers is completely in a molten state.

In another embodiment the one or more melting temperatures is two ormore melting temperatures, wherein the desired temperature is determinedwithin a temperature range or the desired temperature is determined as arange within the temperature range, wherein the temperature range has anupper boundary temperature being less or equal to one of the meltingtemperatures, wherein the temperature range has a lower boundarytemperature being greater or equal to another one of the meltingtemperatures.

This embodiment may be advantageous because it may provide for a simpleand straightforward definition of the optimal texturing processtemperature.

In another embodiment, the upper boundary temperature is no more than apredetermined percentage larger than the lower boundary temperature indegrees Celsius, wherein the predetermined percentage is any one of thefollowing: 5%, 10%, or 15%.

This embodiment may be advantageous because it may provide for a simpledefinition of the optimal process window, because only one meltingtemperature has to be determined using the DSC data (e.g., heat flowversus temperature curve).

The only one melting temperature can be determined using the firstregistered peak of the curve, when the curve is measured by increasingthe temperature. In addition, this embodiment may be advantageousbecause the heating of the monofilament yarn in the step of thetexturing (curling) of the monofilament yarn may be reduced to aminimum, thereby providing for an energy-efficient process.

In another embodiment the other one of the melting temperatures is thelowest of the one or more melting temperatures. The crystalline metingtemperature used in this embodiment can be used as the lower boundarytemperature.

In another embodiment, each of the melting temperatures is a meltingtemperature of the respective polymer.

In another embodiment, the melting temperature of the respective polymeris a minimum temperature at which only a portion of a crystallinefraction of the respective polymer is in a molten state. The portion ofthe crystalline fraction of the polymer can be defined in a range of10%-90% (preferably 25%-75%) by weight of a crystalline fraction of thepolymer.

In another embodiment, the DSC data comprises a heat flow curve versustemperature, wherein the crystalline temperature of the respectivepolymer is a temperature at which a peak of a heat flow curvecorresponding to a melting of a crystalline fraction of the respectivepolymer has its maximum.

This embodiment may be advantageous because it can provide for aneffective approach for determining the melting temperatures.

In another embodiment, wherein at least one of the polymers haspolymorphism, wherein some of the melting temperatures is a meltingtemperature of a respective polymorphic modification of the polymerhaving polymorphism.

In another embodiment the polymer blend comprises first portions eachhaving the respective polymorphic modification, wherein the meltingtemperature of the respective polymorphic modification is a minimumtemperature at which only a portion of the first portion having therespective polymorphic modification is in a molten state. The portion ofthe first portion can be defined in a range of 10%-90%) (preferably25%-75%) by weight of the first portion.

In another embodiment the DSC data comprises a heat flow curve versustemperature, wherein the crystalline temperature of the respectivepolymorphic modification is a temperature at which a peak of the heatflow curve corresponding to a melting of the respective polymorphicmodification has its maximum.

This embodiment may be advantageous because it can provide for aneffective approach for determination of the melting temperatures.

In another embodiment, the DSC data comprises a curve of a heat flowversus temperature in a temperature range, wherein the curve has a baseline, wherein the curve coincides with the base line at a lower boundarytemperature of the temperature range and at an upper boundarytemperature of the temperature range, wherein the upper boundarytemperature and the lower boundary temperature are differenttemperatures, wherein the determined desired temperature complies withthe following constraint: a ratio of an integral value and an overallintegral value is within a predefined range, wherein the integral valueis equal to an integral of a difference of the curve and the base linefrom the lower boundary temperature to the determined desiredtemperature, wherein the overall integral value is equal to an integralof the difference of the curve and the base line from the lower boundarytemperature to the upper boundary temperature. The predefined range canbe 0.05-0.15, preferably 0.09-0.11.

In another embodiment at least two of the polymers are different typesof polyethylene.

This embodiment may be advantageous because polyethylene may havesuperior properties for manufacturing of the textured yarn in comparisonwith other polymers. Particularly, linear polyethylene (e.g. linearlow-density polyethylene (LLDPE) or and high-density polyethylene (HDPE)offers a wide range of physical material properties, covering thetechnical requirements of artificial turf yarn. The density of linearpolyethylene can be widely modified by co-monomers. The molecular weightdistribution can be controlled with catalysts and by polymerizationprocess management. Blending different types of polyethylene broadensthe variability further. In particular, LLDPE is blended, i.e. mixed,with compatible material, such as VLDPE and/or HDPE with densitiesdifferent from LLDPE. It may also be possible to blend different typesof LLDPE.

Utilization of polymer blends comprising different types of polyethylenemay provide for a balance between stability and softness of the texturedyarn. Stability means in this context stiffness, wear resistance,hardness, resilience, etc., whereas softness means flexibility,elasticity, smoothness, etc. Blending different materials each with therequired stability or softness may result in the properties providingthe required balance between stability and softness.

In another embodiment the texturing device comprises a stuffer box.

This embodiment may be advantageous because it may provide for animproved quality of the textured yarn. The nozzle for hot air injectionof the stuffer box can provide for advanced temperature control when thehot air has the temperature within the temperature range of thetexturing process. A turbulent flow of the hot air inside the stufferbox can facilitate the process of texturing (curling).

In another embodiment the texturing device comprises a venturi nozzle.

This embodiment may be advantageous because it may provide for animproved quality of the textured yarn. The monofilament yarn passesthrough the venturi nozzle together with a hot air. The venturi nozzlecan be configured such that the monofilament yarn is textured (curled)by the turbulent flow of the hot air in an exiting throat. Moreover theventuri nozzle can provide for substantial pressure increase in theexiting throat which can facilitate the texturing (curling) process.Injection of the hot air in the venturi nozzle can provide for anadvanced process control when the injected hot air has the temperature.

In another embodiment the texturing device is an air jet texturizingmachine. The air jet texturizing machine can be built as disclosed inthe book “Synthetic Fibers” by Franz Fourné in chapter 4.12.4(“Synthetic Fibers,” Franz Fourne; Carl Hanser Verlag GmbH & Co, 1999,ISBN 10: 3446160728/ISBN 13: 9783446160729, p. 449-452).

In another embodiment the method further comprises raising thetemperature of the monofilament yarn to a temperature within thetemperature range (of the texturing process) using one or more godets.

This embodiment may be advantageous because it may provide for animproved process control, since the monofilament yarn is preheated tothe temperature within the temperature range before the step oftexturing (curling) of the monofilament yarn.

In another embodiment the sample for collecting the DSC data is takenfrom the polymer blend.

This embodiment may be advantageous because it may provide for aneffective determination of the temperature range within which thetexturing (curling) of the monofilament yarn is performed.

In another embodiment the sample for collecting the DSC data is a sampleof the monofilament yarn.

This embodiment may be advantageous because it may provide for aneffective determination of the temperature range within which thetexturing (curling) of the monofilament yarn is performed. For instance,the monofilament yarns can be manufactured using different methods.Executing DSC on different samples can enable selection of anappropriate monofilament yarn.

In another embodiment the method further comprises drawing (stretching)the monofilament yarn, e.g. to a factor of 4-6.5.

This embodiment may be advantageous because it may provide for anincrease in crystallinity of the monofilament yarn (e.g. an increase incrystallinity of at least one of the polymers of the polymer blend usedfor the manufacturing of the monofilament yarn). In the other words, thesize of crystalline portions of the monofilament yarn (or at least oneof the polymers of the polymer blend) is increased relative to the sizeof amorphous portions of the monofilament yarn. As a result themonofilament yarn or at least of the polymers of the polymer blendbecome more rigid. The stretching of the monofilament yarn can furthercause reshaping of fragments (e.g. beads) of one of the polymers of thepolymer blend used for the manufacturing of the monofilament yarn suchthat they have thread like regions, which can make impossibledelamination of different polymers in the monofilament yarn from eachother, in particular when immiscible polymers are used in the polymerblend. This embodiment may also be advantageous, because the drawing(stretching) process of the monofilament yarn can give rise topolymorphism, i.e. crystallographic unit cell modification. For instancethe drawing process can result in forming triclinic crystal modificationof polyethylene in addition to orthorhombic crystal modification ofpolyethylene formed after extruding and cooling.

This drawing of the monofilament yarn causes the monofilament to becomelonger and in the process the fragments of one of the polymers of thepolymer blend (e.g. beads) are stretched and elongated. Depending uponthe amount of stretching the fragments of one of the polymers (e.g.beads) of the polymer blend are elongated more.

In another embodiment the providing of the monofilament yarn comprisesextruding the polymer blend into the monofilament yarn.

This embodiment may be advantageous, because it may provide formanufacturing of the monofilament yarn out of a broad spectrum ofpolymers including immiscible polymers.

In another embodiment the method further comprises creating the polymerblend, wherein the polymer blend is at least a three-phase system,wherein the polymer blend comprises a first polymer, a second polymer,and a compatibilizer, wherein the first polymer and the second polymerare immiscible, wherein the first polymer forms polymer beads surroundedby the compatibilizer within the second polymer.

In a specific example the first polymer could be polyamide and thesecond polymer could be polyethylene. Stretching the polyamide willcause an increase in the crystalline regions making the polyamidestiffer. This is also true for other semi-crystalline plastic polymers.

In another embodiment, the first polymer comprises (or consists of)polyamide (PA) and the second polymer comprises (or consists of)polyethylene (PE). The first polymer may comprise at least 90 weightpercent of PA. The second polymer can comprise at least 90 weightpercent of PE. The polymer mixture can comprise at least 30 weightpercent of PE and/or at least 30 weight percent of PA.

In another embodiment, the first polymer comprises (or consists of)polyester and the second polymer comprises (or consists of) PE. Thefirst polymer may comprise at least 90 weight percent of polyester. Thesecond polymer can comprise at least 90 weight percent of PE. Thepolymer mixture can comprise at least 30 weight percent of PE and/or atleast 30 weight percent of polyester.

In another embodiment, the first polymer comprises (or consists of)polyester and the second polymer comprises (or consists of)polypropylene (PP). The first polymer may comprise at least 90 weightpercent of polyester. The second polymer can comprise at least 90 weightpercent of PP. The polymer mixture can comprise at least 30 weightpercent of PP and/or at least 30 weight percent of polyester.

In another embodiment, the first polymer comprises (or consists of) PAand the second polymer comprises (consists of) PP. The first polymer maycomprise at least 90 weight percent of PA. The second polymer cancomprise at least 90 weight percent of PP. The polymer mixture cancomprise at least 30 weight percent of PP and/or at least 30 weightpercent of PA.

These embodiments related to the polymer blends/mixtures may beadvantageous because it may enable utilization of a broader spectrum ofpolymers for manufacturing of the monofilament yarn such that theproperties of the artificial turf fiber can be tailored. As it ismentioned above different polymers of the polymer blend can provide fordifferent properties of the textured yarn. One polymer can provide forthe stability and/or the resilience (e.g. the ability to spring backafter being stepped or pressed down), while another polymer can providefor the softness (e.g. the softer or a grass-like feel).

These embodiments related to the polymer blends/mixtures may have afurther advantage that the second polymer and any immiscible polymersmay not delaminate from each other. The thread-like regions can beembedded within the second polymer. It is therefore impossible for themto delaminate.

A further advantage may possibly be that the thread-like regions areconcentrated in a central region of the monofilament during theextrusion process. This may lead to a concentration of the more rigidmaterial in the center of the monofilament yarn and a larger amount ofsofter plastic on the exterior or outer region of the monofilament yarn.This may further provide for an artificial turf fiber with moregrass-like properties, when the artificial turf fiber is made of thetextured (curled) monofilament yarn.

A further advantage may be that the artificial turf fibers made of thetextured (curled) monofilament yarn have improved long term elasticity.This may require reduced maintenance of the artificial turf and lessbrushing of the fibers because they more naturally regain their shapeand stand up after mechanical use.

In another embodiment the creating of the polymer blend comprises thesteps of: forming a first blend by mixing the first polymer with thecompatibilizer; heating the first blend; extruding the first heatedblend; granulating the extruded first blend; mixing the granulated firstblend with the second polymer; and heating the granulated first blendwith the second polymer to form the polymer blend. This particularmethod of creating the polymer mixture may be advantageous because itenables very precise control over how the first polymer andcompatibilizer are distributed within the second polymer. For instancethe size or shape of the extruded first mixture may determine the sizeof the polymer beads in the polymer mixture.

This embodiment may be advantageous, because a so called single-screwextrusion method may be used. As an alternative to this, the polymerblend may also be created by putting all of the components that make itup together at once. For instance the first polymer, the second polymerand the compatibilizer could be all added together at the same time.Other ingredients such as additional polymers or other additives couldalso be put together at the same time. The amount of mixing of thepolymer blend could then be increased for instance by using a twin-screwfeed for the extrusion. In this case the desired distribution of thepolymer beads can be achieved by using the proper rate or amount ofmixing.

In another embodiment the polymer blend is at least a four phase system,wherein the polymer blend comprises at least a third polymer, whereinthe third polymer is immiscible with the second polymer, wherein thethird polymer further forms the polymer beads surrounded by thecompatibilizer within the second polymer.

This embodiment may be advantageous because it may enable utilization ofan even broader spectrum of polymers for manufacturing of themonofilament yarn. As it is mentioned above different polymers of thepolymer blend can provide for different properties of the textured yarn.One polymer can provide for the stability, while another polymer canprovide for the softness. This particular embodiment can provide forcombining in a final product properties of at least three polymers.

In another embodiment the creating of the polymer blend comprises thesteps of: forming a first blend by mixing the first polymer and thethird polymer with the compatibilizer; heating the first blend;extruding the first heated blend; granulating the extruded first blend;mixing the first blend with the second polymer; and heating the mixedfirst blend with the second polymer to form the polymer blend.

This embodiment may be advantageous because it may provide for aneffective procedure for manufacturing of the polymer blend comprisingmultiple polymers. As an alternative the first polymer could be used tomake a granulate with the compatibilizer separately from making thethird polymer with the same or a different compatibilizer. Thegranulates could then be mixed with the second polymer to make thepolymer mixture. As another alternative to this the polymer mixturecould be made by adding the first polymer, a second polymer, the thirdpolymer and the compatibilizer all together at the same time and thenmixing them more vigorously. For instance a two-screw feed could be usedfor the extruder.

In another aspect the invention provides for a textured (curled)artificial turf yarn manufactured as described above.

In another aspect the invention provides for a method of manufacturingan artificial turf carpet, wherein the method comprises: manufacturingthe textured artificial yarn as described above; tufting the texturedartificial turf yarn into a backing. The artificial turf backing may forinstance be a textile or other flat structure which is able to havefibers tufted into it. The textured artificial turf yarn may also haveproperties or features which are provided for by any of theaforementioned method steps.

In another aspect the invention provides for an artificial turf carpetmanufactured according to the method for manufacturing of the artificialturf according to the aforementioned embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following embodiments of the invention are explained in greaterdetail, by way of example only, making reference to the drawings inwhich:

FIG. 1 illustrates an example of a system for manufacturing of atextured (curled) monofilament yarn;

FIG. 2 illustrates an example drawing device;

FIG. 3 illustrates an example cross-section of a monofilament yarn;

FIG. 4 illustrates an example cross-section of a monofilament yarn;

FIG. 5 illustrates an example texturing (curling) device;

FIG. 6 illustrates an example stuffer box;

FIG. 7 illustrates an example venturi nozzle;

FIG. 8 illustrates an example DSC curve;

FIG. 9 illustrates an example DSC curve;

FIG. 10 illustrates an example DSC curve;

FIG. 11 shows a flow chart of a method;

FIG. 12 shows a flow chart of a method;

FIG. 13 shows a flow chart of a method;

FIG. 14 shows a flow chart of a method;

FIG. 15 shows a diagram which illustrates a cross-section of a polymerblend;

FIG. 16 shows a diagram which illustrates a cross-section of a polymerblend;

FIG. 17 shows an example of a cross-section of an example of artificialturf.

DETAILED DESCRIPTION

Like numbered elements in these figures are either equivalent elementsor perform the same function. Elements which have been discussedpreviously will not necessarily be discussed in later figures if thefunction is equivalent.

FIG. 1 illustrates an example system of manufacturing of a textured(curled) monofilament yarn 122. The system comprises: an extruder 100(e.g. a screw-extruder) and a filament texturing (curling) device. Thesystem can further comprise one or more drawing devices 115, 118, one ormore thermosetting (or heating) devices (e.g. godets, ovens) 117, one ormore cooling devices (e.g. godets, bathes with cooling liquid) 116, 120,97, and one or more rollers 121.

The extruder 100 comprises at least one hopper 101 for feedingcomponents of a monofilament yarn (e.g. a blend of polymers) into theextruder and one outlet 102 for the monofilament yarn. The outlet 102can be implemented as a wide slot nozzle or a spinneret. A polymer meltformed in a chamber of the extruder is pressed through the outlet 102 toform a monofilament yarn of a specific shape. A fragment of the wideslot nozzle or the spinneret is depicted in FIG. 1.

FIG. 1 illustrates the extrusion of the polymer mixture into amonofilament. Shown is an amount of polymer blend 96. Within the polymerblend 96 there is a large number of portions 138 of a first polymer ofthe polymer blend 96 being at least partially embedded in a secondpolymer 137 of the polymer blend 96. A screw, piston or other device ofthe extruder 100 is used to force the polymer mixture 96 through a hole95 in a plate 102 a. This causes the polymer blend 96 to be extrudedinto a monofilament yarn 119. The monofilament yarn 119 is shown ascontaining fragments 138 of the first polymer of the polymer blend 96also. The both of the polymers of are extruded together.

In some examples the polymer blend can have different compositions.Within the polymer blend 96 there is a large number of polymer beads138. The polymer beads 138 may be made of one or more polymers that isnot miscible with the second polymer 137 and is also separated from thesecond polymer 137 by a compatibilizer. A screw, piston or other deviceis used to force the polymer blend 96 through a hole 95 in a plate 102a. This causes the polymer blend 96 to be extruded into a monofilamentyarn 119. The monofilament yarn 119 is shown as containing polymer beads138 also. The second polymer 137 and the polymer beads 138 are extrudedtogether. In some examples the second polymer 137 will be less viscousthan the polymer beads 138 and the polymer beads 408 will tend toconcentrate in the center of the monofilament yarn 119. This may lead todesirable properties for the final artificial turf fiber as this maylead to a concentration of the thread-like regions in the core region ofthe monofilament yarn 119.

The monofilament yarn can be cooled down after the extrusion using thecooling device 97. When the cooling device is implemented as a godet, itcan comprise two rollers 99 and 98 for winding the monofilament yarn119. The cooling process can be implementing by maintaining atemperature of the rollers 99 and 98 within the specified range and/orby air cooling and/or by water cooling. A temperature of water (or air)can be kept within a specified range as well. Alternatively the coolingdevice can be a bath with a cooling liquid (e.g. water) in which themonofilament yarn is cooled. The monofilament yarn is cooled down usingthe cooling device 97 to a temperature where crystallization can takeplace. In the crystallization process the crystallites are forming to apercentage, which depends on the cooling rate. The higher the coolingrate, the less is the crystallinity and vice versa.

The monofilament yarn can be further drawn using the drawing device 115.The drawing device can comprise three rollers 104, 103, 105. The drawingratio is defined as the ratio of linear speeds of a pair of rollers 103and 104 (or 104 and 105). The drawing device 115 can be operable forheating the monofilament yarn 119 during or before the drawing process.This can be implemented by heating one or more the rollers in order tokeep their temperature within a predetermined temperature range and/orby air heating, wherein the hot air has a temperature within apredetermined temperature range. The elongation of the monofilament yarnin the drawing device can force the macromolecules of the monofilamentyarn to parallelize. This results in a higher degree of crystallinityand increased tensile strength, compared with undrawn monofilament yarn.

FIG. 2 depicts an alternative implementation 115 a of any of the drawingdevices mentioned herein (e.g. the drawing device 115 or 118). Thedrawing device comprises one or more feeding rollers 81-83, an oven 80,and one or more receiving rollers 84-86. The one or more feeding rollersare configured to feed the monofilament yarn 119 into the oven. The oneor more receiving rollers are configured to receive the monofilamentyarn from the oven. The oven is configured to heat the monofilamentyarn. The drawing ratio is determined by a ratio of the linear speeds ofthe feeding roller 83 being the last roller before the oven and thereceiving roller 84 being the first after oven. The thermosettingprocess (drawing process) is performed in the oven 80, in which themonofilament yarn in stretched and heated simultaneously.

FIG. 3 depicts a not to scale cross-section of a segment themonofilament yarn 136 before its processing in the drawing device 115,whereas FIG. 4 depicts a not to scale cross-section of a segment of themonofilament yarn 140 after its processing in the drawing device 115.Before the drawing process the fragments of the first polymer 138 canhave an arbitrary shape, e.g. a shape of beads. The fragments of thefirst polymer are at least partially incorporated in the second polymer137. After the drawing process the fragments of the first polymer 138have elongated shape in comparison to the fragments of the first polymer128 before the drawing process.

The monofilament yarn can be further cooled using the cooling device116. The cooling device, when implemented as a cooling godet can haverollers 106 and 107. The cooling device can be built and/or function inthe same way as the cooling device 97. Afterwards the monofilament yarncan be further drawn using the drawing device 118 having rollers 110,111, and 112. The drawing device 118 can be built and/or function in thesame way as the drawing device 115.

The monofilament yarn can be further heated using one or more heatingdevices 117. The heating device 117, when implemented as a godet,comprises a pair of rollers 108 and 109. The heating of the monofilamentyarn can be made by keeping a temperature of the rollers within apredetermined temperature range and/or by hot air having a temperaturewithin a predetermined temperature range. A temperature sensor 113positioned in-between the heating godet 117 and the texturing (curling)device 114 can be used as a feedback temperature sensor for providingfeedback to the heating godet 117 in order to provide a temperature ofthe monofilament yarn within a temperature range required for thetexturing (curling) process. The temperature sensor 113 can beconfigured to measure the temperature of the monofilament yarn byregistering infrared radiation of the monofilament yarn.

A controller 70 is configured to control a process temperature of thetexturing process in the texturing device 114. The controller 70comprises a computer processor 72 and memory 73 comprising instructionsexecutable by the computer processor. The controller is communicativelycoupled to the texturing device 114, the temperature sensor 113, and theheating device 117. The communicative coupling can be implemented via acomputer network 71. The controller is operable to hold an actualtemperature of a texturing process in the texturing device at a desiredtemperature which is required for the texturing process. The desiredtemperature can be specified as a temperature range. In this case theholding of the actual temperature at the desired temperature compriseskeeping the actual temperature within the specified range, in particularthe actual temperature is kept as close as possible to a middletemperature of the temperature range. The middle temperature is equal toan average of a lower boundary of the temperature range and an upperboundary of the chosen temperature range. The temperature of thetexturing process can be determined by at least one of the followingfactors: a temperature of the monofilament yarn, a temperature in atexturing device component, in which the texturing process takes place,and a temperature of a texturing device component, which is in physicalcontact with the monofilament yarn in the texturing process. Theexecution of the computer instructions by the computer processor 72causes the controller to hold the process temperature at the desiredtemperature. The control of the process temperature can be implementedas follows. The controller reads out the temperature of the monofilamentyarn registered by the temperature sensor 113. The temperature of themonofilament yarn is used as a feedback signal for setting thetemperature of the heating device 117 in order to provide the heating ofthe monofilament yarn to the desired temperature. The functioning ofthis feedback loop can be implemented using aproportional-integral-derivative algorithm. In addition the controllercan provide temperature setting signals to the texturing device and/orother devices operable for changing the temperature of the texturingprocess. This can be implemented in the same way as the aforementionedfeedback loop, i.e. by reading one or more temperature values registeredby one or more temperature sensors of the texturing device and providingthe feedback signal to the texturing device and/or the other device forholding a temperature in the texturing device at the desiredtemperature. The feedback signal can be provided to the texturing deviceand/or any other device operable for changing a temperature of thetexturing process. The functioning of this feedback loop can beimplemented using the proportional-integral-derivative algorithm aswell. The controller can be configured to operate the aforementionedfeedback loops independently on in conjunction with each other.

After the heating using one or more heating devices 117 the monofilamentyarn is textured (curled) in the texturing (curling) device 114. Thetextured (curled) monofilament yarn 122 is cooled using a cooling godet120. The cooling can be performed by keeping a temperature of a roller120 of the cooling godet within a predetermined temperature range and/orby air having a temperature within a predetermined temperature range.The textured monofilament yarn 122 can be forwarded further to anotherroller 121 for further processing.

The sequence of optional processing units, i.e. the cooling godet 97,the drawing device 115, the cooling godet 116, the drawing device 118,the heating godet 117, can be different. It depends on particularprocessing steps required for preprocessing steps before the texturing(curling) process. Additional drawing devices, and/or heating devices,and/or cooling devices can be included. For instance several heatingdevices can be used instead of the single heating device 117 depicted inFIG. 1 in order to provide for a gradual heating of the monofilamentyarn 119. Alternatively, the preprocessed monofilament yarn can be usedfor the texturing (curling). In this case there can be no need of theextruder 100, the cooling devices 97 and 116, and the drawing device115. When drawing process can be executed in several steps, severaldrawing devices 115 can be used in series.

FIG. 5 depicts an example of a texturing (curling) device 114 a. Thedevice 114 a comprises a pair of toothed wheels 123 and 124 configuredto press the monofilament yarn 119 in-between the toothed wheels suchthat profile of the toothed wheels is imprinted in the monofilament yarn119 in order to cause its texturing (curling). The tooth profile thetoothed wheels can have triangular shape depicted in FIG. 5 or smooth.Alternatively it can be a smooth wave like profile. The device 114 a canhave more than one pair of the toothed wheels, wherein the monofilamentyarn is processed sequentially by the pairs of wheels. The temperaturecontrol of the texturing process can be implemented by one or more ofthe following: controlling, as described above, the temperature of themonofilament yarn entering the texturing device (e.g. using thecontroller 70, temperature sensor 113, and the heating device 117);controlling a temperature of the toothed wheels (e.g. by using thecontroller 70, which can be configured to read out temperature of one ormore temperature sensors operable for registering the temperature of thetoothed wheels and sending a feedback signal to one or more heatersoperable for heating the toothed wheels).

FIG. 6 depicts another example of a texturing (curling) device 114 b.The device 114 b is a stuffer box. The stuffer box comprises a hollowchamber 129 having an inlet 126 for the monofilament yarn 119 and anoutlet 127 for the textured monofilament yarn 122. The hollow chambercan have a conical shape, wherein a diameter of the hollow chamber nearthe inlet 126 is smaller than the diameter of the hollow chamber nearthe outlet 127. The inlet 119 and the outlet 127 can be positioned atthe opposite sides of the hollow chamber 129. An air inlet nozzle 125for injecting air into the hollow chamber 129 is attached to an upperportion of the hollow chamber 129, i.e. in the proximity of the inlet126. The lower portion of the hollow chamber 129 comprises slits 128 forair exhaust, i.e. the slits are located in the proximity of the outlet127. The air inlet nozzle 125 and the slits 128 are configured toprovide a turbulent flow of the air inside the hollow chamber 129. Theturbulent air flow causes tension of the monofilament yarn during thetexturing (curling) process. The temperature of the texturing processand the turbulent flow are configured to cause texturing (curling) ofthe monofilament yarn 119. The temperature control of the texturingprocess performed by the device 114 b can be implemented by one or moreof the following: controlling, as described above, the temperature ofthe monofilament yarn entering the texturing device (e.g. using thecontroller 70, temperature sensor 113, and the heating device 117);controlling the temperature of air, which is injected into the air inletnozzle 125. The controller 70 can be configured to maintain the airtemperature at the desired temperature by reading out temperature of oneor more temperature sensors operable for registering a temperature ofthe hot air and sending a feedback signal to one or more heatersoperable for heating the air.

FIG. 7 depicts another example of a texturing (curling) device 114 c.The device 114 c is a venturi nozzle. The venturi nozzle comprises anentrance throat 131 and an exiting throat 132. An inlet 130 for themonofilament yarn 119 is mounted on a first end of the entrance throat.An outlet 135 for the textured (curled) monofilament yarn is mounted ona first end of the exiting throat 132. A second end of the entrancethroat is attached to a second end of the exiting throat. An area of across-section of the first end of the entrance throat is bigger than anarea of a cross-section of the second end of the entrance throat. Anarea of a cross-section of the first end of the exiting throat is biggerthan an area of a cross-section of the second end of the exiting throat.The entrance throat 131 can have an air inlet. Alternatively the inlet119 can be configured not only for passing the monofilament yarn intothe venturi nozzle, but for injecting air as well. The exiting throat132 has slits 134 for air exhaust. The venturi nozzle is configured suchthat the air injected into the entrance throat via inlet port 130 or airinlet 133 flows into the exiting throat 132, wherein the air flow isturbulent in the exiting throat. The turbulent air flow causes tensionof the monofilament yarn during the texturing (curling) process. Inaddition, the air flow from the entrance throat into the exiting throatcauses substantial pressure increase in the upper portion of the exitingthroat, i.e. in the portion located between the slits 124 and the secondend of the exiting throat. The slits 134 can facilitate the turbulentflow of the air in the upper portion of the exiting throat and/or thepressure increase. The temperature control of the texturing processperformed by the device 114 c can be implemented by one or more of thefollowing: controlling, as described above, the temperature of themonofilament yarn entering the texturing device (e.g. using thecontroller 70, temperature sensor 113, and the heating device 117);controlling the temperature of air, which is injected into the air inlet133 and/or air inlet port 130. The controller 70 can be configured tomaintain the air temperature at the desired temperature by reading outtemperature of one or more temperature sensors operable for registeringa temperature of the hot air and sending a feedback signal to one ormore heaters operable for heating the air. At least one of the followingfactors causes/facilitates the texturing (curling) of the monofilamentyarn: the air temperature, the turbulent air flow, and the pressuredrop.

The textured (curled) monofilament yarn, which can be used as theartificial turf fibers can be prepared from a polymer blend comprisingat least two polymers. The polymer blend can be a more complex mixture.The polymer blend can be at least a three phase system. It can comprisea first polymer, a second polymer, and a compatibilizer. Thesecomponents form a three-phase system. The first and a second polymer areimmiscible. If there are additional polymers or compatibilizers are usedin the polymer blend, then the three phase system may be increased to afour, five or more phase system. The first polymer could be polyamideand the second polymer could be polyethylene. The polymer blend cancomprise a polar polymer and a non-polar polymer. The polymer blend cancomprise at least one of the following: polyethylene terephthalate,which is also commonly abbreviated as PET, polybutylene terephthalate,which is also commonly abbreviated as PBT, polyethylene, polypropylene.

The compatibilizer can be any one of the following: a maleic acidgrafted on polyethylene or polyamide; a maleic anhydride grafted on freeradical initiated graft copolymer of polyethylene, SEBS, EVA, EPD, orpolyproplene with an unsaturated acid or its anhydride such as maleicacid, glycidyl methacrylate, ricinoloxazoline maleinate; a graftcopolymer of SEBS with glycidyl methacrylate, a graft copolymer of EVAwith mercaptoacetic acid and maleic anhydride; a graft copolymer of EPDMwith maleic anhydride; a graft copolymer of polypropylene with maleicanhydride; a polyolefin-graft-polyamide; and a polyacrylic acid typecompatibilizer.

For instance, the textured (curled) monofilament yarn, which can be usedas the artificial turf fibers can be prepared from polyethylene basedpolymers. Different polyethylene (type) based polymers are blended suchthat a desired property profile is created. The main focus hereby lieson the crimp properties of the monofilament yarn.

The polymer blend can comprise LLDPE and HDPE. LLDPE is a copolymer ofethylene and α-olefin or 1-olefin. Several 1-olefins can becopolymerized together with ethylene, but most of the commerciallyavailable LLDPEs are copolymers with 1-butene, 1-hexene or 1-octene, ormixtures thereof, as co-monomers. In a polymerization process, both themonomer ethylene and the co-monomer 1-olefin are incorporatedstep-by-step into a growing macromolecular chain. In each single stepeither an ethylene molecule or a 1-olefin molecule is added to thechain.

The sequence of ethylene and 1-olefin units along the chain isdetermined by both, the polymerization catalysts and the details of thereaction layout, such as pressure, temperature, etc. In general, thereare two distinctive types of catalysts; multi-site catalysts andsingle-site catalysts. The type of catalyst controls the polymerizationprogress and the way in which monomers and co-monomers are added to thepolymer chain. Polymers are always entities of macromolecules withdifferent chain length, distributed around an average value. Polymersare thus characterized by a molecular weight distribution. Differentaverage values can be defined depending on statistical methods. Inpractice two averages are used, denoted as M_(n) and Mw. M_(n) is thenumber average of the molecular weight distribution, mathematicallyexpressed by

M _(n) =Σn _(i) M _(i) /Σn _(i)

MW is the weight average of the molecular weight distribution and isrelated to the fact that heavier molecules contribute more to thearithmetic average than the lighter ones. This is mathematicallyexpressed by

Mw=Σn _(i) M _(i) ² /Σn _(i) M _(i)

The polydispersity index PDI is the ratio of Mw/M_(n) and indicates thebroadness of the distribution. In general, polymers prepared withmulti-site catalysts have a greater PDI than those prepared withsingle-site catalysts.

Moreover, the chemical composition of the macromolecules depends on thetype of catalyst. As mentioned above, every 1-olefin or α-olefin can actas a co-monomer in the polymerization process, but typically only1-butene, 1-hexene and 1-octene is in use for copolymerization of LLDPE.As these molecules carry a double bond between two carbon atoms, it ispossible to insert them instead of an ethylene molecule into the growingchain of the macromolecule which forms in the polymerization process.The incorporation of a 1-olefin molecule into the polymer main chainleaves, other than ethylene does, a side chain on the main chain.1-butene, for instance, includes 4 carbon atoms and generates an ethylside chain, whereas two carbon atoms (the two with the double bondbetween carbon atoms 1 and 2) are incorporated into the main chain andanother two carbon atoms extent outwardly of that main chain as a sidechain. In case of 1-hexene the length of the side chain is 4 carbonatoms and it is 6 with 1-octene. Concerning the side chain distribution,the molecular architecture may greatly be influenced by the choice ofthe catalyst used in the polymerization process. Multi-site catalysts,also referred to as Ziegler or Ziegler-Natta catalysts or Phillipscatalysts, yield in heterogeneously branched polymers, whereassingle-site catalysts, also referred to as metallocene catalysts, yieldin homogeneously branched polymers. In heterogeneously branchedmacromolecules the distance from one branching point to anotherbranching point is broadly distributed along the polymer main chain. Theother way round, the branches are more evenly spaced in homogeneousbranched LLDPEs. It has also been observed that with Ziegler catalyststhe co-monomers are preferably incorporated into the short length mainchains, while the longer main chains deplete of co-monomers. Dependingon the design of the polymerization process the side chain branching isheterogeneous or homogeneous.

The use of multi-site catalysts results in polymers with relativelybroad molecular weight distributions compared with single-sitecatalysts. Moreover, the molecular weight distribution can be influencedby using a cascaded reactor layout, leading to polymers with multimodalmolecular weight distributions. Blending different types of polyethylenein situ, i.e. inside the polymerization reactor, or ex situ, i.e. afterpolymerization, broadens the variety further.

Number, length and distribution of the side chains in PE macromoleculesgreatly influence the properties and the processability. According toapplicant's experience, it is advantageous to use LLDPE with a broaddistribution of side chains, typical for Ziegler-catalyzed, solutionpolymerized polymers for turf fiber production, in particular fortexturized turf fiber production. The fraction of short length polymerchains with high branching makes the fibers, produced of theseLLDPE-types, easy to texturize. In the course of the texturizing processthe fibers need to be softened under the influence of heat and thendeformed, such that a wanted crimped shape results and stays on thefibers. It has turned out that the above mentioned LLDPE-types areappropriate for this process.

Preferably, in the texturizing (curling) process a certain fraction ofthe polymeric filament (i.e. monofilament yarn) must be in a moltenstate, i.e. the small crystallites of the structure have lost theirordered state, whereas another fraction has not. This means, that thefilaments ought to be stable enough not to adhere or lump and deformableenough to crimp under the impact of heat and mechanical deformation.Once the deformation is achieved, the filaments are quenched giving riseto crystallization of the small crystallites. Thereby the texturizingstays in the filaments.

Texturizing is supported by both, the chemical structure of thepolymeric filaments and the temperature of the filaments at the momentof deformation. Both can be appraised by knowledge of the meltingbehavior of the polymeric filaments. The melting behavior manifests in acharacteristic melting graph detected by DSC. In a characteristicmelting graph, measured by DSC, the variation of the melt enthalpy (heatflow) over time, i.e. dH/dt is plotted against the variation intemperature over time, i.e. dT/dt. The melt enthalpy ΔH or heat offusion can be calculated by mathematical integration, i.e. thedetermination of the area between the baseline and the complete curve orparts thereof. This reflects the amount of heat necessary to completelyor partially melt the sample.

Polymers herein are generally of the type of partially crystallinesubstances. Partially crystalline polymers are characterized in that apart thereof is solid crystals, while the rest is amorphous. Theamorphous part behaves as a highly viscous liquid. Liquid parts of apolymer sample do not contribute to the melting process. The meltingcurve as detected by DSC reflects the melting behavior of thecrystallites.

Number and size of the crystallites determine the density of polymers.LLDPE has a lower density compared with HDPE. Combining LLDPE and HDPEinto a blend may have the advantage to broaden the melting curve. Themelting curves of LLDPE are quite specifiable, depending on what type ofLLDPE is regarded. As already mentioned, the co-monomer, the catalystand the type of process layout have a great influence on the appearanceof the melting curve. There are three types of processes for thepreparation of LLDPE: slurry, solution and gas-phase. The slurry-processis underrepresented in this context, as very few LLDPE-types exist. But,it is the method of choice of the production of HDPE. LLDPE fromsolution processes is characterized in that mostly 1-octene acts asco-monomer in that process.

Contrariwise 1-hexene and 1-butene are the co-monomers used in gas-phaseprocesses.

The composition of an example polymeric blend used for manufacturing ofthe textured (curled) monofilament yarn comprises:

-   -   (A) 10% by weight of the total composition to 95% by weight of        the total composition of at least one LLDPE having        -   a density of 915 to 920 grams per liter,        -   a melt index (I₂) from 1 to 10 grams per 10 minutes,        -   a polydispersity Mw/M_(n) in a range of 3-5, in particular,        -   1-olefin comonomers, the comonomers being 1-butene, 1-hexene            or 1-octene or compositions thereof,        -   a heterogeneously or homogeneously side branching            distribution,        -   a melting graph as measured by DSC with one, two or three            maxima in the temperature range between 30° C. and 150° C.,            wherein the number of maxima is determined by a number of            polymorphic modifications of the LLDPE used in this example            polymeric blend, the maxima can be isothermal, overlapping,            or co-located; and    -   (B) 10% by weight of the total composition to 30% by weight of        the total composition of at least one HDPE having        -   a density of 935 to 960 grams per liter,        -   a melt index (I₂) from 1 to 10 grams per 10 minutes,        -   a polydispersity index Mw/M_(n) in a range of 3-6, in            particular,        -   1-olefin comonomers, the comonomers being 1-butene, 1-hexene            or 1-octene or compositions thereof,        -   a heterogeneously side branching distribution,        -   a melting graph as measured by DSC with one maximum in the            temperature range between 30° C. and 150° C.

The polymeric blends used for the manufacturing of the (texturized)filaments are characterized by a melting graph measured by DSC. The DSCmethod is widely used for thermal analysis. The method offers a fast andeasy determination of phase transitions, e.g. melting, glass transition,and crystallization of polymer samples.

In a DSC analysis the energy is measured as a heat flow into or out ofthe sample. The vertical axis of a DSC plot is given in units of mW ormJ/s, whereas the horizontal axis shows the temperature in ° C. In a DSCrun the sample is placed in a small metal pan and the measured againstan empty metal pan. The temperature is raised (or lowered) at a constantrate dT/dt, mostly 10° C./min or 20° C./min and the pans are heatedseparately. When a phase transition occurs in the sample the uptake ofenergy (or the release of energy) is compensated by the furnace underthe sample pan as long as necessary to maintain the heating (or cooling)rate and recorded as the energy flow. As the experiment is always doneunder constant pressure the energy flow is represented by a change inenthalpy ΔH. Then dH/dt equals C_(p) dT/dt, wherein C_(p) is the heatcapacity of the sample.

The enthalpy of the complete melting process ΔH can be calculated bymathematical integration of the DSC trace, i.e. ΔH=∫(dH) dT. Therefor abaseline (which is not plotted automatically throughout a DSC run) isneeded. This baseline has to be interpolated as flat baseline, when theDSC curve follows the same progression in the segments of the curvebefore and after the phase transition. However this is often not thecase, because C_(p) may not be the same before and after the phasetransition, moreover C_(p) can depend on temperature. In cases, where astep in C_(p) is present, an interpolation using sigmoid function issuitable for the construction of the baseline. The interpolationreflects the extent of progress of the transition. At each point of theinterpolated baseline, i.e. each temperature in the region of the peak,difference in C_(p) is calculated by linear extrapolation of the leftpre-transition side and the right post-transition side of the curve andthen weighted by the extent of progress of the transition. Besidesinterpolation using sigmoid function interpolation using other functionslike cubic of step functions can be used.

Once the baseline has been constructed, a left and a right limit for theintegral must be defined, which gives rise to another discussion. Whenanalyzing LLDPE with the DSC-method, the left limit is often hard tofind in the temperature range between ambient and end of melting. Thisis because LLDPE may be partly melted at ambient temperatures. A coolingdevice and a purge gas device are necessary to extend the range totemperatures lower than ambient.

An example DSC graph is depicted in FIG. 8. The DSC graph representsschematically an example curve 232 of a heat flow (W) versustemperature. A peak 230 of the curve 232 corresponds to a melting of aone polymer of the blend (e.g. polymer 138). This polymer is calledfurther in the description related to this figure as the first polymer.A peak 231 of the curve 232 corresponds to a melting of another polymerof the blend (e.g. polymer 137). This polymer is called further in thedescription related to this figure as the second polymer. The first andthe second polymers do not have polymorphism. The curve 232 has thefollowing characteristic temperatures: Ts01 (234), Ts1 (220), Tm1 (221),Tf1 (222) Tf01 (235), Ts02 (236), Ts2 (223), Tm2 (224), Tf2 (225), Tf02(237).

Each peak of the curve 232 has the following characteristictemperatures:

a) Ts01 (Ts02) is a temperature at which the curve 233 starts to deviatefrom the base line 233. This temperature characterizes the beginning ofthe melting process;

b) Ts1 (Ts2) is a temperature characterizing substantial beginning ofthe melting process. At this temperature a substantial portion of thecrystalline fraction of the first (second) polymer is molten. As usualthis temperature is called a lower boundary of a melting range of amelting process or a melting point. The temperature Ts1 (Ts2) is atemperature at which the tangent line 227 (228) intersects the base line233. The tangent line 227 (228) is a tangent to a left slope of the peak230 (231). The tangent line has the same first derivative as the leftslope of the peak at a temperature at which the left slope of the peak230 (231) has its second derivative equal to zero;

c) Tm1 (Tm2) is a temperature at which the peak 230 (231) has itsmaximum. This temperature (as usual) indicates the temperature at whichthe melting process has the highest rate;

d) Tf1 (Tf2) is a temperature characterizing substantial ending of themelting process. At this temperature the crystalline fraction of thefirst (second) polymer is almost completely molten. As usual thistemperature is called an upper boundary of the melting range of themelting process. The temperature Tf1 (Tf2) is a temperature at which thetangent line 226 (229) intersects the base line 233. The tangent line226 (229) is a tangent to a right slope of the peak 230 (231). Thetangent line has the same first derivative as the right slope of thepeak at a temperature at which the right slope of the peak 230 (231) hasits second derivative equal to zero;

e) Tf01 (Tf02) is a temperature at which the curve 233 starts tocoincide with the base line 233. This temperature characterizes thecomplete end of the melting process. At this temperature the crystallinefraction of the first (second) polymer is completely molten.

The dashed line 233 is a base line of the DSC curve. The base line ofthe peak 230 is straight, because the melting of the crystallinefraction of the first polymer does not result in a change in the heatcapacity (Cp) of the first polymer and as a result thereof in the changeof the heat capacity of the polymer blend. The base line of the peak 231is a sigmoidal baseline because the melting of the crystalline fractionof the second polymer results in a change in the specific heat capacityof the second polymer and as a result thereof in the specific heatcapacity of the polymer blend. The sigmoidal base line can be anysuitable sigmoidal function.

The parameters used for determination of a process window of texturing(curling) of the monofilament yarn can be derived using the followingdefinitions and/or procedures.

First the DSC curve can be preprocessed. The contribution of the baseline can be subtracted from the original DSC curve. In other words eachvalue of the preprocessed DSC curve at a particular temperature is equalto a value of the original DSC curve at said temperature minus a valueof the baseline curve at said temperature. For further steps, either theoriginal or the preprocessed DSC curve can be used. In case when peaksof the DSC curve overlap, a deconvolution of the overlapping peaks canbe performed in order to provide processing of each of the overlappingpeaks in an independent way. Afterwards the temperatures specified insections a)-e) are determined.

The lower (upper) boundary value of the temperature range for thetexturing (curling) process can be one of the following temperatures:Ts01, Ts1, Tm1, Tf1, Tf01, Ts02, and Ts2 (Ts1, Tm1, Tf1, Tf01, Ts02,Ts2, Tm2), wherein the lower boundary value is less than the upperboundary value. For instance, the temperature range Tf01-Ts02 can beselected when it is required that the crystalline fraction of the firstpolymer is completely molten and the crystalline fraction of the secondpolymer is completely in the solid state in the process of the texturing(curling) of the monofilament yarn. Alternatively, the temperature rangeTf01-Tm2 can be selected, when it is required that the crystallinefraction of the first polymer is completely molten and the crystallinefraction of the second polymer is partially molten in the process of thetexturing (curling) of the monofilament yarn. As yet anotheralternative, the temperature range Tm1-Tf1 can be selected, when it isrequired that the crystalline fraction of the first polymer is partiallymolten and the crystalline fraction of the second polymer is completelyin the solid state in the process of the texturing (curling) of themonofilament yarn. As yet another alternative Tm1 can be taken as areference temperature TR for the texturing (curling) process. Since thetemperature of the filaments should not fall below the referencetemperature TR during the course of texturizing the filaments, a lowerboundary and an upper boundary of the temperature range can be definedas follows: the lower boundary is equal to TR and the upper boundary isequal to a surplus temperature Ts, wherein the surplus temperature Tsbeing no more than a predetermined percentage larger than the lowerboundary temperature in degrees Celsius, wherein the predeterminedpercentage is 15%, preferably 10%, and more preferably 5%.

Another example DSC graph is depicted in FIG. 9. The DSC graphrepresents schematically an example curve 411 of a heat flow (W) versustemperature. The DSC curve is a cooling or heating curve of a polymerblend comprising two different polymers each having no polymorphism. Inthis example the melting temperatures of the polymers of the blend areclose to each other. As a result thereof the curve 411 has only onemaximum at Tm2 temperature 425. Merely for illustrative purposes a baseline 410 of the curve 411 is flat (a horizontal line). Alternatively thecurve 411 can be a preprocessed curve having contribution of thenon-flat base line (e.g. the base line 233 in FIG. 8) subtracted fromthe original DSC curve.

Being not bound to the example curve depicted in FIG. 9 the overlappingpeaks constituting an integral DSC curve can be extracted using adeconvolution procedure. The deconvolution can be performed for instanceusing the Stokes method with Gaussian smoothing, the method based ondecomposition of a DSC curve into a Fourier series, or the method basedon the decomposition of a DSC curve into a linear combination ofinstrumental functions. After extraction of the overlapping peaks eachof them can be processed as described above.

Deconvolution of the curve 411 results in the generation of two curves412 and 413 each representing a respective peak. One curve (e.g. 412) isa characteristic of a melting process of one of the polymers of theblend, while the other curve (e.g. 413) is a characteristic of a meltingprocess of the other polymer of the blend. As clearly seen from FIG. 9the peaks represented by the curves 412 and 413 overlap. The curves 412and 413 can be further processed in the same way as described above.Processing of the curve 412 results in determination of the followingparameters: Ts01 temperature 418 having the same physical meaning as theTs01 temperature 234 or the Ts02 temperature 236 in FIG. 8; Ts1temperature 419 having the same physical meaning as the Ts1 temperature220 or the Ts2 temperature 223 in FIG. 8, wherein Ts1 temperature 419 isdetermined using a tangent line 414 in the same way as Ts1 temperature220 is determined using the tangent line 227; Tm1 temperature 420 havingthe same physical meaning as the Tm1 temperature 221 or the Tm2temperature 224 in FIG. 8; Tf1 temperature 421 having the same physicalmeaning as the Tf1 temperature 222 or the Tf2 temperature 225 in FIG. 8,wherein the Tf1 temperature 421 is determined using the tangent line 415in the same way as Tf1 temperature 222 is determined the tangent line226; Tf01 temperature 422 having the same physical meaning as the Tf01235 temperature or the Tf02 237 temperature in FIG. 8. Processing of thecurve 413 results in determination of the following parameters: Ts02temperature 423 having the same physical meaning as the Ts01 temperature234 or the Ts02 temperature 236 in FIG. 8; Ts2 temperature 424 havingthe same physical meaning as the Ts1 temperature 220 or the Ts2temperature 223 in FIG. 8, wherein Ts2 temperature 419 is determinedusing a tangent line 416 in the same way as Ts1 temperature 220 isdetermined using the tangent line 227; Tm2 temperature 425 having thesame physical meaning as the Tm1 temperature 221 or the Tm2 temperature224 in FIG. 8; Tf2 temperature 426 having the same physical meaning asthe Tf1 temperature 222 or the Tf2 temperature 225 in FIG. 8, whereinthe Tf2 temperature 426 is determined using the tangent line 416 in thesame way as Tf1 temperature 222 is determined the tangent line 226; Tf01temperature 427 having the same physical meaning as the Tf01 temperature235 or the Tf02 temperature 237 in FIG. 8.

The lower (upper) boundary value of the temperature range for thetexturing (curling) process can be selected in the same way as describedabove.

Another example DSC graph is depicted in FIG. 10. The DSC graphrepresents schematically a curve 218 of a heat flow (W) versustemperature. In contrast to polymer blend which DSC curve depicted inFIG. 8, one polymer of a polymer blend has two polymorphic modificationsand another one polymer of a polymer blend does not have polymorphism.The polymer having polymorphism is called further as the third polymerin the description of FIG. 10. The polymer having no polymorphism iscalled further as the fourth polymer in the description of FIG. 10. Peak215 corresponds to a melting of one of the polymorphic modifications ofthe third polymer. Peak 216 corresponds to a melting of another one ofthe polymorphic modifications of the third polymer. Peak 217 correspondsto a melting of a crystalline fraction of the fourth polymer. The baseline curve 219 is defined in the same way as described above. Tm3 (201),Tm4 (204), and Tm5 (207) are defined as specified above in section c).Ts3 (200), Ts4 (203), Ts5 (206) are defined using tangent lines 210,211, and 213 as specified above in section b). Tf3 (202), Tf4 (205), Tf5(208) are defined using tangent lines 209, 212, and 214 as specifiedabove in section d). The temperatures equivalent to Ts01 and Tf01 aredefined as specified above in points a) and e). These temperatures arenot depicted in FIG. 10 merely for illustrative purposes. Ts5, Tm5, Tf5have the same physical meaning as Ts2, Tm2, and Tf2. Ts3 and Tf4 havethe same physical meaning as Ts1 and Tf2. In contrast to Ts1, Tm1, andTf1 which characterize the melting process of entire crystallinefraction of the first polymer, Ts3, Tm3, and Tf3 (Ts4, Tm4, and Tf4)characterize the melting process of only one of the polymorphicmodifications of the third polymer. Ts3, Tm3, and Tf3 (Ts4, Tm4, andTf4) have the same physical meaning for the characterization of themelting process of the polymorphic modification as Ts1, Tm1, and Tf1 forthe characterization of the melting process of the crystalline fractionof the polymer.

In the example depicted in FIG. 10 the lower (upper) boundary value ofthe temperature range for the texturing (curling) process can be one ofthe following temperatures: Ts3, Tm3, Tf3, Ts4, Tm4, Tf4 and Ts5 (Tm3,Tf3, Ts4, Tm4, Tf4, Ts5, and Tm5), wherein the lower boundary value isless than the upper boundary value. For instance, the temperature rangeTf4-Ts5 can be selected when it is required that the crystallinefraction of the third polymer is almost completely molten and thecrystalline fraction of the fourth polymer is almost completely in thesolid state in the process of the texturing (curling) of themonofilament yarn. Alternatively, the temperature range Tm3-Tf3 can beselected, when it is required that the only one of the polymorphicmodifications of the third polymer is substantially molten and the restof the crystalline fraction of the polymer blend is in a solid state inthe process of the texturing (curling) of the monofilament yarn. As yetanother alternative, the temperature range Ts4-Tm4 can be selected, whenit is required that the one of the polymorphic modifications of thethird polymer is completely molten, another one of the polymorphicmodifications of the third polymer is only partially molten, and thecrystalline fraction of the fourth polymer is in the solid state in theprocess of the texturing (curling) of the monofilament yarn. As yetanother alternative Tm4 can be taken as a reference temperature TR forthe texturing (curling) process. Since the temperature of the filamentsshould not fall below the reference temperature TR during the course oftexturizing the filaments, a lower boundary and an upper boundary of thetemperature range can be defined as follows: the lower boundary is equalto TR and the upper boundary is equal to a surplus temperature Ts,wherein the surplus temperature Ts being no more than a predeterminedpercentage larger than the lower boundary temperature in degreesCelsius, wherein the predetermined percentage is 15%, preferably 10%,and more preferably 5%.

Independent from a particular structure of a DSC curve (e.g. number ofpeaks, overlapping/non overlapping peaks, etc.) another approach can beused for determination of the temperature range used for texturing(curling) process. The lower boundary Tl of the temperature range isdetermined according to the following equation:

${\frac{\int_{Ts}^{Tl}{\left( {{{Heat}\mspace{14mu} {flow}\; (T)} - {{Base}\mspace{14mu} {line}\mspace{14mu} (T)}} \right){dT}}}{\int_{Ts}^{Tf}{\left( {{{Heat}\mspace{14mu} {flow}\; (T)} - {{Base}\mspace{14mu} {line}\mspace{14mu} (T)}} \right){dT}}} = {\alpha 1}},$

and the upper boundary Tu is determined according to the followingequation:

$\frac{\int_{Ts}^{Tu}{\left( {{{Heat}\mspace{14mu} {flow}\; (T)} - {{Base}\mspace{14mu} {line}\mspace{14mu} (T)}} \right){dT}}}{\int_{Ts}^{Tf}{\left( {{{Heat}\mspace{14mu} {flow}\; (T)} - {{Base}\mspace{14mu} {line}\mspace{14mu} (T)}} \right){dT}}} = {{\alpha 2}.}$

Heat flow (T) is the original DSC curve (e.g. DSC curve 411 in FIG. 9).Base line (T) is a temperature dependent base line of the original DSCcurve (e.g. base line 410 in FIG. 9). Ts is a lower boundary of atemperature range of the DSC curve (e.g. Ts (428) in FIG. 9). At thistemperature the DSC curve coincides with its base line. Tf is an upperboundary of a temperature range of the DSC curve (e.g. Tf (428) in FIG.9). At this temperature the DSC curve coincides with its base line. Thefollowing constrains apply for the equations above: Ts<Tf, 0<α1<α2<1. α1can be equal to 0.05, preferably to 0.09. α2 can be equal to 0.15,preferably to 0.11. The melting temperature Tm (e.g. Tm 429 in FIG. 9)can be determined as Tl<Tm<Tu. At Tm 429 a portion of a crystallinefraction of one of the polymers of the polymer blend and a portion of acrystalline fraction of the other one of the polymers of the polymerblend are in a molten state and another portion of the crystallinefraction of the one of the polymers of the polymer blend and anotherportion of the crystalline fraction of the other one of the polymers ofthe polymer blend are in a solid state.

With independent of the particular temperature range selected as thetemperature range of the texturing process the desired temperature canbe determined as a middle temperature of the selected temperature range.The desired temperature is equal to an average of an upper boundary ofthe selected temperature range and the lower boundary of the selectedtemperature range. The desired temperature can be used as the setting ofthe controller 70, i.e. be used as the desired temperature therein. Inaddition or as alternative the desired temperature can be specified asthe selected temperature range or a range within the selectedtemperature range (e.g. a subrange of the selected temperature range).

FIG. 11 illustrates a flowchart diagram of a method for manufacturing ofa textured (curled) monofilament yarn, which can be used as a textured(curled) artificial turf yarn. The method can be executed using devicesdepicted in FIG. 1. The method begins with process block 600, wherein amonofilament yarn is provided. The monofilament yarn comprises a polymerblend of two or more polymers. As it is mentioned above the polymerblend can comprise immiscible polymers and at least one compatibilizer.Process block 602 is executed after 600. In process block 602 DSC datais received. The data comprises DSC data of a sample of the polymerblend measurement using a DSC system. The data characterizes meltingprocess of different polymers of the blend. The data can furthercharacterize melting processes of different polymorphic modifications ofone of the polymers of the blend, if said polymer has polymorphicmodifications. The sample can be a sample of the monofilament yarn.Alternatively the sample can be taken from the polymer blend used formanufacturing of the monofilament yarn.

Process block 604 is executed after process block 602. In process block604 one or more melting temperatures of the monofilament yarn aredetermined using the DSC data. The determination of the meltingtemperatures can be performed as described above, by determiningbaseline, temperatures corresponding to maxima of the DSC curve, etc.Afterwards the desired temperature of the texturing process isdetermined using the one or more melting temperatures. Process block 606is executed after process block 604. In process block 606 themonofilament yarn is textured (curled) using the texturing device toprovide the textured artificial yarn, the controller 70 is programmed tohold the actual temperature at the determined desired temperature. As itis mentioned above the melting temperature can be a melting temperatureof a crystalline fraction of the polymer of the blend. In case with thepolymer of the blend has polymorphism, then the melting temperature canbe a melting temperature of one of its polymorphic modifications.

The desired temperature can be selected within the following temperatureranges, preferably in the middle of the respective temperature rangewithin which the desired temperature is selected. The temperature rangecan selected such that a portion of a crystalline fraction of thepolymer blend is in a solid state in a process of the texturing(curling) of the monofilament yarn and another portion of thecrystalline fraction of the polymer blend is in a molten state. Thelower boundary of such a temperature range can be any of the followingtemperatures depicted on FIGS. 8-10: Ts1, Tm1, Tf1, Tf01, Ts02, Ts2,Ts3, Tm3, Tf3, Ts4, Tm4, Tf4, Ts5. The upper boundary of such atemperature range can be any of the following temperatures depicted onFIGS. 8-10: Tm1, Tf1, Tf01, Ts02, Ts2, Tm2, Tm3, Tf3, Ts4, Tm4, Tf4,Ts5, Tm5. The upper and the lower boundary temperatures have to beselected such that the upper boundary is greater than the lowerboundary. Alternatively the upper boundary Tu and the lower boundary TIcan be determined according to the aforementioned equations.

Alternatively, the temperature range can be selected such that acrystalline fraction of one of the polymers is in a solid state in aprocess of the texturing (curling) of the monofilament yarn and acrystalline fraction of another one of the polymers is in a molten statein the process of the texturing (curling) of the monofilament yarn. Theupper boundary of such a temperature range can be Ts02 depicted in FIG.8 and the lower boundary temperature of such a temperature range can beTf01 depicted in FIG. 8.

The temperature range can have a lower boundary temperature beinggreater or equal to one of the melting temperatures, which can be lowestone of the melting temperatures determined in process block 604 (e.g.Tm3). The temperature range can have an upper boundary temperature beingless or equal another one of the melting temperatures, which can be thehighest one of the melting temperatures determined in process block 604(e.g. Tm5). According to the DSC data obtained for different polymerblends (in particular for the polymer blend comprising LLDPE and HDPE)an optimal temperature range for texturing (curling) can be 90-110degrees Celsius.

As it is mentioned above, DSC curves provide plenty of information fordetermination of the melting temperatures which are used for thedetermination of the temperature range of the texturing (curling) of themonofilament yarn. For instance, the melting temperature of the polymercan be determined as a minimum temperature at which only a portion of acrystalline fraction of the respective polymer is in a molten state(e.g. Ts1, Tm1, Tf1, Ts2, Tm2, Tf2, Ts3, Tm3, Tf3, Ts4, Tm4, Tf4, Ts5,Tm5, Tf5). In case when the polymer has polymorphism, the meltingtemperature can be determined as a minimum temperature at which only aportion of its polymorphic modification is in a molten state (e.g. Ts3,Tm3, Tf3 for the melting of the polymorphic modification which meltingprocess corresponds to the peak 215 in FIG. 10; Ts4, Tm4, Tf4 for themelting of the polymorphic modification which melting processcorresponds to the peak 216 in FIG. 10). Alternatively or in additionthe melting temperature can be determined as a temperature at which theDSC curve has its maximum (e.g. Tm1, Tm2, Tm3, Tm4, Tm5).

With independent of different approaches for selection/determination ofthe temperature range and/or the desired temperature for the texturing(curling) process, the temperature range and/or the desired temperatureare selected such that only a portion of a crystalline fraction of thepolymer blend in molten in the texturing (curling) process. Withindependent of the particular temperature range selected for thetexturing process, the desired temperature can be determined as a middletemperature of the temperature range of the texturing process, i.e. asan average value of an upper boundary of the temperature range and lowerboundary of the temperature range. In addition or as alternative thedesired temperature can be determined as said temperature range or arange within the temperature range, wherein preferably theaforementioned average value is comprised in the range within thetemperature range.

The texturing (curling) of the monofilament yarn can be performed forinstance using any of the texturing (curling) devices depicted in FIGS.5-7. In addition an air jet texturing device can be used for thetexturing (curling) process. Any of these devices can be operated suchthat texturing (curling) is made within the temperature range of thetexturing process. This can be implemented by setting a desiredtemperature of the controller 70 to the desired temperature determinedin process block 604. When the filament texturing (curling) device 114 ais used, the controller 70 can be configured to control as describedabove the temperature of the toothed wheels (e.g. 123 and 124) and/orthe temperature of the monofilament yarn entering the texturing device.When the stuffer box 114 b is used for the texturing (curling) of themonofilament yarn in process block 606, the controller can be configuredto control the temperature of the air injected through the nozzle 125and/or the temperature of the monofilament yarn entering the texturingdevice 114 b. When the venturi nozzle 114 c is used for the texturing(curling) of the monofilament yarn in process block 606, the controllercan be configured to control the temperature of the monofilament yarnentering the texturing device 114 c and/or the temperature of the airinjected into the venturi nozzle through the air inlet 133 and/or inputport 130. When the air jet texturizing device is used for the texturing(curling) of the monofilament yarn in process block 606, the controllercan be configured to control the temperature of the monofilament yarnentering the air jet texturizing device and/or the temperature of thecompressed air injected into the air jet texturizing device. When theaforementioned thread-like regions are present in the monofilament yarnbefore the texturing (curling) the thread-like regions are present inthe textured (curled) monofilament yarn.

Turning back to FIG. 11, an optional process block 606 a can be executedbefore process block 606, preferably immediately before 606 processblock. In process block 606 a the temperature of the monofilament yarnis increased to a temperature within the temperature range of thetexturing process using one or more heating devices (e.g. the heatingdevice 117). In order to implement this process block the sensor 113,the controller 70, and the heating device can be used as describedabove.

Another optional process block 608 can be executed after process block606, preferably immediately after process block 608. The textured(curled) monofilament yarn is cooled. The cooling can be performed usinga cooling godet 120. The cooling can an a quenching procedure, whereinthe textured (curled) monofilament yarn can be cooled down to atemperature of 20-25 degrees Celsius within 1-5 seconds.

FIG. 12 illustrates a flow chart diagram of a method for manufacturingof a monofilament yarn, which can be used in the method which flow chartis shown in FIG. 11. The method begins with process block 620. Inprocess block 620 the polymer blend is created. The polymer blend cancomprise two different types of polyethylene (e.g. LLDPE and HDPE). Thepolymer blend can be a more complex system. For instance it can be atleast a three-phase system. In this case it can comprise a firstpolymer, a second polymer and a compatibilizer. The first polymer andthe second polymer are immiscible. In other examples there may beadditional polymers such as a third, fourth, or even fifth polymer thatare also immiscible with the second polymer. There also may beadditional compatibilizers which are used either in combination with thefirst polymer or the additional third, fourth, or fifth polymer. Thefirst polymer forms polymer beads surrounded by the compatibilizer. Thepolymer beads may also be formed by additional polymers which are notmiscible in the second polymer. The polymer beads are surrounded by thecompatibilizer and are within the second polymer or mixed into thesecond polymer.

Process block 622 is executed after process block 620. In process block622 the polymer blend is extruded into a monofilament yarn. Thisextrusion can be performed using the extruder 100 depicted in FIG. 1.The polymer blend is feed into the extruder 100 via inlet 101. Insidethe extruder 100 the polymers of the polymer blend are completely moltenand the individual parts of the blend are homogeneously mixed. Thepolymer melt is pressed through a spinneret (or a wide slit nozzle) 102,102 a, whereby filaments of a specific shape are formed.

Process block 624 is executed after process block 622. The filaments are(rapidly) cooled down to a temperature where crystallization can takeplace. In the crystallization process the crystallites are forming to apercentage, which depends on the cooling rate. The higher the coolingrate, the less is the crystallinity and vice versa. Process block 624can be executed using the cooling device 97 depicted in FIG. 1.

Process block 626 is executed after process block 624. In process block626 the monofilament yarn is drawn e.g. to a factor of 4-6, i.e. themonofilament yarn is elongated 4-6 times. The preferred drawing ratio is1:5.6. During the drawing process the monofilament yarn is heated to atemperature. The temperature can be at least 10-20 degrees Celsius(preferably 70-100 degrees Celsius for a polymer bled comprisingPolyamide (PA) and/or Polyethylene (PET)) below the temperature of thelast maximum on the DSC curve (e.g. Tm3 in FIG. 10) of the polymer blendused for the manufacturing of the monofilament yarn drawn in processblock 626. The temperature of the last maximum on the DSC curve is thetemperature being the last in the sequence determined in process block604. Process block 626 can be executed using the drawing device 115 or115 a. The drawing of the monofilament yarn forces the macromolecules toparallelize. This results in a higher degree of crystallinity andincreased tensile strength after cooling, compared with undrawnfilaments. In addition the drawing process can reshape the polymer beadssuch that the reshaped beads have thread-like regions.

Process block 628 is executed after process block 626. In process block628 the monofilament yarn is cooled again. This can be done in the sameway as in process block 624. The cooling godet or cooling drum 116 canbe used for performing the cooling in process block 628.

Process block 630 is executed after process block 628. In process block630 the monofilament yarn is drawn e.g. to a factor of 1.1-1.3. Thepreferable drawing ratio is 1:1.2. During the drawing process themonofilament yarn is heated to a temperature. The temperature can be thesame as in Process block 626. Process block 630 can be executed usingthe drawing device 118. Execution of process block 630 can result inrelaxation of stress in the monofilament yarn.

FIG. 13 shows a flowchart which illustrates one method of creating thepolymer blend which can be used for manufacturing of the monofilamentyarn, e.g. according to the method which flow chart is shown in FIG. 12.In other the other words, the method which flow chart is shown in FIG.13 can be an extension or alternative of process block 620. In thisexample the polymer mixture is a three-phase system and comprises thefirst polymer, a second polymer and the compatibilizer. The polymerblend may also comprise other components such as additives to color orprovide flame or UV-resistance or improve the flowing properties of thepolymer blend. First in step 640 a first blend is formed by mixing thefirst polymer with the compatibilizer. Additional additives may also beadded during this step. Next in step 642 the first blend is heated. Nextin step 644 the first blend is extruded. Then in step 646 the extrudedfirst blend is then granulated or chopped into small pieces. Next instep 648 the granulated first blend is mixed with the second polymer.Additional additives may also be added to the polymer blend at thistime. Finally in step 650 the granulated first blend is heated with thesecond polymer to form the polymer blend. The heating and mixing mayoccur at the same time. The polymer blend created in process block 650can be further processed in the same way as the polymer blend created inprocess block 620.

FIG. 14 shows a flowchart which illustrates a further example of how tocreate a polymer blend for manufacturing of the monofilament yarn, e.g.according to the method which flow chart is shown in FIG. 12. In otherwords, the method which flow chart is shown in FIG. 14 can be anextension or alternative of process block 620. In this example thepolymer blend additionally comprises at least a third polymer. The thirdpolymer is immiscible with the second polymer and the polymer blend isat least a four-phase system. The third polymer further forms thepolymer beads surrounded by the compatibilizer with the second polymer.First in step 660 a first blend is formed by mixing the first polymerand the third polymer with the compatibilizer. Additional additives maybe added to the first blend at this point. Next in step 662 the firstblend is heated. The heating and the mixing of the first blend may bedone at the same time. Next in step 664 the first blend is extruded.Next in step 666 the extruded first blend is granulated or chopped intotiny pieces. Next in step 668 the first blend is mixed with the secondpolymer. Additional additives may be added to the polymer blend at thistime. Then finally in step 670 the heated first blend and the secondpolymer are heated to form the polymer blend. The heating and the mixingmay be done simultaneously. The polymer blend created in process block670 can be further processed in the same way as the polymer blendcreated in process block 620.

FIG. 15 shows a diagram which illustrates a cross-section of a polymerblend 400. The polymer blend 400 comprises a first polymer 402, a secondpolymer 404, and a compatibilizer 406. The first polymer 402 and thesecond polymer 404 are immiscible. The first polymer 402 is lessabundant than the second polymer 404. The first polymer 402 is shown asbeing surrounded by compatibilizer 406 and being dispersed within thesecond polymer 404. The first polymer 402 surrounded by thecompatibilizer 406 forms a number of polymer beads 408. The polymerbeads 408 may be spherical or oval in shape or they may also beirregularly-shaped depending up on how well the polymer blend is mixedand the temperature. The polymer blend 400 is an example of athree-phase system. The three phases are the regions of the firstpolymer 402. The second phase region is the compatibilizer 406 and thethird phase region is the second polymer 404. The compatibilizer 406separates the first polymer 402 from the second polymer 406.

FIG. 16 shows a further example of a polymer blend 500. The exampleshown in FIG. 16 is similar to that shown in FIG. 15 however, thepolymer mixture 500 additionally comprises a third polymer 502. Some ofthe polymer beads 408 are now comprised of the third polymer 502. Thepolymer blend 500 shown in FIG. 14 is a four-phase system. The fourphases are made up of the first polymer 402, the second polymer 404, thethird polymer 502, and the compatibilizer 406. The first polymer 402 andthe third polymer 502 are not miscible with the second polymer 404. Thecompatibilizer 406 separates the first polymer 402 from the secondpolymer 404 and the third polymer 502 from the second polymer 404. Inthis example the same compatibilizer 406 is used for both the firstpolymer 402 and the third polymer 502. In other examples a differentcompatibilizer 406 could be used for the first polymer 402 and the thirdpolymer 502.

The third of the first polymer can be a polar polymer. The third of thefirst polymer can be for instance polyamide. Alternatively the third orthe first polymer can be polyethylene terephthalate or polybutyleneterephthalate.

The polymer blend can comprise between 1% and 30% by weight the firstpolymer and the third polymer combined. In this example the balance ofthe weight may be made up by such components as the second polymer, thecompatibilizer, and any other additional additives put into the polymermixture.

Alternatively the polymer blend can comprise between 1 and 20% (orbetween 5% and 10%) by weight of the first polymer and the third polymercombined. Again, in this example the balance of the weight of thepolymer mixture may be made up by the second polymer, thecompatibilizer, and any other additional additives.

The polymer blend can comprise between 1% and 30% by weight the firstpolymer. In this example the balance of the weight may be made up forexample by the second polymer, the compatibilizer, and any otheradditional additives.

Alternatively the polymer blend can comprises between 1% and 20% (orbetween 5% and 10%) by weight of the first polymer. In this example thebalance of the weight may be made up by the second polymer, thecompatibilizer, and any other additional additives mixed into thepolymer mixture.

The second polymer can be a non-polar polymer. The second polymer can bepolyethylene or polypropylene. The polymer blend can comprise between80-90% by weight of the second polymer. In this example the balance ofthe weight may be made up by the first polymer, possibly the secondpolymer if it is present in the polymer mixture, the compatibilizer, andany other chemicals or additives added to the polymer mixture.

The polymer blend can further comprise any one of the following: a wax,a dulling agent, a ultraviolet stabilizer, a flame retardant, ananti-oxidant, a pigment, and combinations thereof. These listedadditional components may be added to the polymer blend to give theartificial turf fibers made of the textured (curled) monofilament yarnother desired properties such as being flame retardant, having a greencolor so that the artificial turf more closely resembles grass andgreater stability in sunlight.

The thread-like regions can be embedded in the second polymer of thetextured (curled) monofilament yarn. The textured monofilament yarn cancomprise a compatibilizer surrounding each of the thread-like regionsand separating the first polymer from the second polymer. Thethread-like regions can have a diameter of less than 20 (or 10)micrometer. Alternatively the thread-like regions can have a diameter ofbetween 1 and 3 micrometer. The thread-like regions can have a length ofless than 2 mm in longitudinal direction of the monofilament yarn.

The textured (curled) monofilament fiber can be used as artificial turffiber for manufacturing of an artificial turf. The textured (curled)monofilament fiber can be incorporated into an artificial turf backingof the artificial turf. This can be implemented for instance by tuftingor weaving the artificial turf fiber (i.e. the textured (curled)monofilament yarn) into the artificial turf backing. After theincorporation of the artificial turf fibers a further optional processcan be performed, wherein the artificial turf fibers are bound to theartificial turf backing. For instance the artificial turf fibers may beglued or held in place by a coating or other material. Alternatively aliquid backing (e.g. latex or polyurethane) can be applied on thebackside of the artificial turf backing such that the liquid backingwets the lower portions of the fiber and firmly includes the fiber afterthe solidification of the backing and thus causing a sufficient tuftlock.

FIG. 17 shows an example of a cross-section of an example of artificialturf 146. The artificial turf 146 comprises an artificial turf backing142. Artificial turf fiber 145 has been tufted into the artificial turfbacking 142. A coating 143 is shown on the bottom of the artificial turfbacking 142. The coating may serve to bind or secure the artificial turffiber 145 to the artificial turf backing 142. The coating 143 may beoptional. For example the artificial turf fibers 145 may bealternatively woven into the artificial turf backing 142. Various typesof glues, coatings or adhesives could be used for the coating 143.

1. A method of manufacturing a textured artificial turf yarn using a texturing device and a controller operable to hold an actual temperature of a texturing process in the texturing device at a desired temperature, wherein the method comprises: providing a monofilament yarn, wherein the monofilament yarn includes a polymer blend of polymers; receiving differential scanning calorimetry, DSC, data of a sample of the polymer blend; determining one or more melting temperatures of the monofilament yarn using the DSC data; determining a desired temperature of the texturing process using the one or more melting temperatures; and texturing the monofilament yarn using the texturing device to provide the textured artificial turf yarn, wherein the controller is programmed to hold the actual temperature at the determined desired temperature-.
 2. The method of claim 1, wherein the desired temperature of the texturing process is determined such that a portion of a crystalline fraction of the polymer blend is in a solid state in a process of the texturing of the monofilament yarn and another portion of the crystalline fraction of the polymer blend is in a molten state in the process of the texturing of the monofilament yarn.
 3. The method claim 1, wherein the one or more melting temperatures is two or more melting temperatures, wherein the desired temperature is determined within a temperature range or the desired temperature is determined as a range within the temperature range, wherein the temperature range has an upper boundary temperature being less or equal to one of the melting temperatures, wherein the temperature range has a lower boundary temperature being greater or equal to another one of the melting temperatures.
 4. The method of claim 3, wherein the upper boundary temperature is no more than a predetermined percentage larger than the lower boundary temperature in degrees Celsius, wherein the predetermined percentage is any one of the following: 5%, 10%, and 15%; and wherein the another one of the melting temperatures is the lowest of the one or more melting temperatures.
 5. (canceled)
 6. The method of claim 1, wherein each of the one or more melting temperatures is a melting temperature of the respective polymer.
 7. The method of claim 6, wherein the melting temperature of the respective polymer is a minimum temperature at which only a portion of a crystalline fraction of the respective polymer is in a molten state.
 8. The method of claim 6, wherein the DSC data includes a curve of a heat flow versus temperature, wherein the crystalline temperature of the respective polymer is a temperature at which a peak of the curve corresponding to a melting of a crystalline fraction of the respective polymer has its maximum.
 9. The method of claim 1, wherein at least one of the polymers has polymorphism, wherein each of some of the melting temperatures is a melting temperature of a respective polymorphic modification of the polymer having polymorphism.
 10. The method of claim 9, wherein the polymer blend includes first portions each having the respective polymorphic modification, wherein the melting temperature of the respective polymorphic modification is a minimum temperature at which only a portion of the first portion having the respective polymorphic modification is in a molten state.
 11. The method of claim 9, wherein the DSC data includes a curve of a heat flow versus temperature, wherein the crystalline temperature of the respective polymorphic modification is a temperature at which a peak of the curve corresponding to a melting of the respective polymorphic modification has its maximum.
 12. The method of claim 1, wherein the desired temperature of the texturing process is determined such that a crystalline fraction of one of the polymers is in a solid state in a process of the texturing of the monofilament yarn and a crystalline fraction of another one of the polymers is in a molten state in the process of the texturing of the monofilament yarn; and/or at least two of the polymers are different types of polyethylene; and/or wherein the texturing device includes a stoffer box or a venturi nozzle; and/or wherein the sample is either a sample of the polymer blend or a sample of the monofilament yarn; and/or wherein the method further includes drawing the monofilament yarn to a factor of 4-6.5; and/or wherein the providing of the monofilament yarn including extruding the polymer blend into the monofilament yarn.
 13. The method of claim 1, wherein the DSC data includes a curve of a heat flow versus temperature in a temperature range, wherein the curve has a base line, wherein the curve coincides with the base line at a lower boundary temperature of the temperature range and at an upper boundary temperature of the temperature range, wherein the upper boundary temperature and the lower boundary temperature are different temperatures, wherein the determined desired temperature complies with the following constraint: a ratio of an integral value and an overall integral value is within a predefined range, wherein the integral value is equal to an integral of a difference of the curve and the base line from the lower boundary temperature to the determined desired temperature, wherein the overall integral value is equal to an integral of the difference of the curve and the base line from the lower boundary temperature to the upper boundary temperature.
 14. The method of claim 13, wherein the predefined range is 0.05-0.15, preferably 0.09-0.11.
 15. (canceled)
 16. (canceled)
 17. (canceled)
 18. The method of claim 3, wherein the method further includes raising the temperature of the monofilament yarn to a temperature within the temperature range using one or more godets.
 19. (canceled)
 20. (canceled)
 21. (canceled)
 22. (canceled)
 23. The method of claim 1, the method further comprising: creating the polymer blend, wherein the polymer blend is at least a three-phase system, wherein the polymer blend includes a first polymer, a second polymer, and a compatibilizer, wherein the first polymer and the second polymer are immiscible, wherein the first polymer forms polymer beads surrounded by the compatibilizer within the second polymer.
 24. The method of claim 23, wherein the creating of the polymer blend comprises: forming a first blend by mixing the first polymer with the compatibilizer; heating the first blend; extruding the first heated blend; granulating the extruded first blend; mixing the granulated first blend with the second polymer; and heating the granulated first blend with the second polymer to form the polymer blend.
 25. The method of claim 24, wherein the polymer blend is at least a four phase system, wherein the polymer blend includes at least a third polymer, wherein the third polymer is immiscible with the second polymer, wherein the third polymer further forms the polymer beads surrounded by the compatibilizer within the second polymer.
 26. The method of claim 25, wherein the creating of the polymer blend comprises: forming a first blend by mixing the first polymer and the third polymer with the compatibilizer; heating the first blend; extruding the first heated blend; granulating the extruded first blend; mixing the first blend with the second polymer; and heating the mixed first blend with the second polymer to form the polymer blend.
 27. A textured artificial turf yarn manufactured according to the method claimed in claim
 1. 28. A method of manufacturing an artificial turf carpet, wherein the method includes: manufacturing the textured artificial yarn according to the method claimed claim 1; tufting the textured artificial turf yarn into a backing.
 29. (canceled) 